Mounting the cutter's mandrel is your first step and I guess I should've started with that.
It's dangerous to assume.
Anytime you remove the ring-cutter from the router, it must be indicted again when you reinstall it.
I use a dedicated set-up and my ring-cutter stays in the router.
I check it periodically to confirm that it hasn't moved. The collet can be 'funny'.
Don't assume that your mandrel is running true when/because it's tightened into the collet.
It might not be. The marriage btwn the mandrel and collet sometimes requires finding the 'sweet-spot'.
Loosen the collet-nut, rotate the mandrel, tighten and indicate it again.
That reading should tell you if you're headed in the right direction.
It's there, you just have to find it.
.015" TIR is HUGE.
However, it's the easiest to identify and the easiest to correct.
Mount your ring-cutter in the router and indicate the side of the saw/wing-cutter, whichever you're using.
Rotate the spindle by hand and take your reading. Zero TIR is your goal.
Anything more than that will be reflected in the thickness of the ring you're parting-off.
If you're advancing your compound to cut a .030" thick ring and the parted ring is .026/.027", something is off.
My router is dead and the brgs are shot but I can still get the saw to run true within .0005".
Knowing this, I just advance my compound an additional .001" and my parted ring is to size.
Back to my previous post; run-out and bad entry-angle are killers.
They each can/will generate heat and destroy your work.
Wood tends to be a little forgiving. Sterling silver set into phenolic, not so much.
It can bring you to tears.
HTHs, KJ
